The present invention relates to an apparatus for controlling voltage-charge controlled power semiconductor devices in equipments for converting electric power, which comprises members adapted to detect function parameters of a said power semiconductor device and an arrangement adapted to control the voltage between the gate and the emitter of the power semiconductor device depending upon the value of the function parameters detected so as to by that control the power semiconductor device.
Voltage-charge controlled power semiconductor devices means power semiconductor devices being voltage controlled during the static state thereof, i.e. when they are conducting or blocking, primarily through the voltage applied between the gate and the emitter of the power semiconductor device, and charge controlled during the very switching process between the static states, since a considerable transport of charges to and from the gate is required as a consequence of the existing capacitances for changing the voltage between the gate and the emitter.
It is here pointed out that all types of such power semiconductor devices are included, such as for example IGBTs (Insulated Gate Bipolar Transistor) and MOSFETs (Metal-Oxide-Semiconductor-Field-Effect-Transistor), in which xe2x80x9cemitterxe2x80x9d and xe2x80x9ccollectorxe2x80x9d in the claims and in the description are to be given a broad sense and comprise also corresponding layers or regions of semiconductor devices, where these have another name, such as Drain and Source, respectively.
Said equipments for converting electric power may be of any type, such as network converters, motor inverters, battery chargers and the like, and they have one thing in common, namely that the power semiconductor devices included therein normally have to be controlled exactly with a very high frequency, i.e. the control has to have a high speed, preferably with reaction times within the nanosecond range.
It is particularly important to have this speed upon occurrence of different faults in the very equipment or in the power semiconductor devices and for being able to take care of certain protection functions, so that possibly damages of the power semiconductor devices or other parts included in the equipment and by that costly breakdowns may be avoided, or the extension of such damages may be remarkably restricted so as to keep the costs for repairs low.
Examples of objects of such a control is to achieve an overvoltage protection of the power semiconductor device upon short-circuiting, control of so called recovery phenomena of a free-wheeling diode associated with the power semiconductor device, optimising switching losses and control of the development of the collector-emitter-voltage and the collector current over the time.
Apparatuses of this type already known have been based on analogous feedbacks from the collector and the emitter of the power semiconductor device so as to form a close analogous regulating circuit or loop so as to control the turn on and turn off process and protect the power semiconductor device. Thus, a parameter-rich interaction between the power semiconductor device controlled and the analogous functions of the control apparatus takes place. Such a control apparatus designed in this way is connected to a problem that in such a construction of the control apparatus it is not possible to make it universal, i.e. manufacture a control apparatus which may be used for controlling different power semiconductor devices or for different applications. Different power semiconductor devices have for sure unique properties, and in combination with different main circuits of the apparatus in question a large amount of regulating objects are created, so that unique adjusting of the regulating hardware of the apparatus is required each time and a unique hardware has then to be produced. Furthermore, different demands on function characteristics such as voltage and current differential coefficients produces in different uses of said equipments a high number of unique adjustments of the control apparatus, and each time these requirements are changed a control apparatus having a unique hardware has to be manufactured.
The object of the present invention is to provide an apparatus of the type defined in the introduction, which is so designed that it may be considered as universal, i.e. it may be used for controlling power semiconductor devices with different properties and be used where different demands are put out from the application side.
This object is according to the invention obtained by arranging said members in such an apparatus to detect selected parameters describing the function of the power semiconductor device through connections to the power semiconductor device, and the apparatus also comprises means adapted to compare the value of the selected function parameters detected with reference levels thereof, a programmable circuit adapted to generate said reference levels for the comparison and process data resulting from the comparison so as to based thereon on its output deliver a digital signal corresponding to an order of a predetermined current level to or from the gate of the power semiconductor device, and a digitally controlled amplifier being current stiff, i.e. provided with current sources operating in constant current mode, adapted to receive the digital signal from the programmable circuit and on basis thereof through said current sources generate a current to or from the gate of the power semiconductor device with said predetermined current level for controlling the power semiconductor device.
By the fact that the control apparatus in this way manages without any analogous, closed feedbacks and it instead uses an indirect determination of the behaviour desired of the power semiconductor device, the control apparatus may be used for different power semiconductor devices in various different main circuits or equipments. This is achieved by a control of the power semiconductor device through the control of the current to and from the gate of the device depending upon the value of selected important function parameters in which it is extremely important that this current may be rapidly controlled or being able to choose this alternative instead of the closed feedbacks already known, and this is made possible by utilising a current stiff converter being digitally controlled and adapted to receive a digital signal from the programmable circuit and on the basis thereof generate the current arrived at by the programmable circuit on the basis of the results of the comparison of the parameters detected with said reference level.
The advantages of a device of the type according to the invention with respect to the control apparatuses already known and described above are many. The amount of necessary hardware when producing said equipments as well as when manufacturing and using the control apparatus is reduced, which means that test equipment has not to be modified each time new demands on the function of the control apparatus arises. Furthermore, the same control apparatus may be used in different equipments, so that the amount of different control apparatuses as well as the storing capacity needed when manufacturing them as well as the number of different spare parts are reduced. Furthermore, the documentation of changes of a construction of the control apparatus as well as the maintenance costs for the control apparatus are reduced as a consequence thereof.
Moreover, a flexibility with respect to the possibilities to adapt the function of the control apparatus to different uses, such as different voltage systems, different power semiconductor devices and different converter equipments, is obtained through the programmability, so that for example a new hardware may replace a broken hardware or a control apparatus going out of production. The only requirement is that the mechanical interface of the control apparatus to the environment is maintained. Furthermore, buyers may change power semiconductor devices after some time, when the previous device has gone out of production as a result of improvements and modifications. Several problems arising in the use may be solved by reprogramming the very hardware instead of replacing the hardware by a new or a corrected one. The programmability results also in the fact that an autonomic test of the control card on which the control apparatus is arranged may be achieved by utilising the programmable circuit. Further advantages are also there. According to preferred embodiments of the invention said members have connections to the collector, the gate and the emitter of the power semiconductor device for detecting the collector-emitter-voltage and the gate-emitter-voltage, respectively, of the power semiconductor device as the said selected parameter. It is also suitable to determine the time differential coefficient of the collector current of the power semiconductor device, in which this in a preferred embodiment of the invention may be done by arranging an auxiliary emitter connection to the emitter of the power semiconductor device closer to the latter than the so called main emitter connection for avoiding a parasitic inductance of the main emitter connection at the connection of the measuring member to the power semiconductor device and measure the voltage created between the auxiliary and the main emitter connection so as to obtain a measure of the time differential coefficient of the collector current by the fact that the programmable circuit uses the parameters detected in this way for designing an order of a predetermined current level to or from the gate of device the turn on, turn off, and protection process of the power semiconductor device may efficiently be controlled.
According to a preferred embodiment of the invention the programmable circuit has a component for connection of an arrangement for reconfiguration of the programmable circuit, i.e. reprogramming of the programmable circuit. The advantages thereof appear from the discussion above. The programmable circuit is according to another preferred embodiment of the invention adapted to enable a change of protecting control functions and adjustment of said reference levels through said programming connection after putting said equipment into service. It will in this way be possible to all the time gradually adapt the control apparatus to possible demands of the user changing or to new power semiconductor devices when old such ones are replaced.
According to another preferred embodiment of the invention the apparatus comprises members for providing feeding direct voltages for the function of the apparatus, and it has a member adapted to supervise the feeding direct voltages to different parts of the apparatus and inform the programmable circuit about the status thereof. The programmable circuit may in this way consider these feeding voltages when elaborating the orders thereof.
According to another preferred embodiment of the invention it comprises a protecting arrangement adapted to protect the power semiconductor device against uncontrollable turn on upon drop out of the feeding direct voltages by keeping the voltage between the gate and the emitter of the power semiconductor device below the level required for activating the power semiconductor device during a period of time in which such feeding direct voltages are not delivered to the apparatus. It may by this be avoided that the power semiconductor device is destroyed when operation faults occur.
According to another preferred embodiment of the invention the amplifier has a first set of current sources adapted to deliver a current of mutually different intensity to the gate of the power semiconductor device and a second set of current sources adapted to generate a current of mutually different intensity from the gate of the power semiconductor device and members adapted to control these current sources on the basis of the digital signal from the programmable circuit for controlling the power semiconductor device. The control of the power semiconductor device may in this way take place with a required high speed, i.e. within the nanosecond range, by changing the current generated by said current sources to and from the gate of the power semiconductor device that quick.
According to another preferred embodiment of the invention, which constitutes a further development of the embodiment last mentioned, the programmable circuit is adapted to deliver said digital signal in the form of a multiple bit word, in which each bit corresponds to a separate of said current sources, in the amplifier, and the current values of the different current sources are bit-weighted. The digital information from the programmable circuit may by this rapidly be D/A converted to predetermined current values resulting from the comparison mentioned above to or from the gate of the power semiconductor device without any requirement of any time for D/A-conversion except for the time for activating current sources.
According to another preferred embodiment of the invention, which also constitutes a further development of the embodiment with two sets of current sources, each said current source comprises a couple of bipolar transistors, a first of which is adapted to have a voltage applied between the collector and the emitter thereof and its base connected to the input of the amplifier for receiving a digital signal with a voltage level well defined and a second is connected by its base to the collector of the first one and by its collector to the gate of the power semiconductor device for generating a current to or from the gate, and both transistors are connected to always be in the linear operation range or be switched off depending upon if a digital xe2x80x9c1xe2x80x9d or xe2x80x9c0xe2x80x9d is received on the base of the first transistor, in which the first transistor is adapted to drive the second one. By connecting the two transistors of the respective couple to each other in this way the second transistor and by that the current delivered thereby to the gate of the power semiconductor device may be changed, i.e. be controlled, with a required high speed, by the fact that the bipolar transistors may rapidly be switched on and off when they are in the linear operation range.
Further advantages as well as advantageous features of the invention will appear from the following description and the other dependent claims.